sequences: cache_value, log_cnt, is_cycled columns

I was just wondering, what are the "cache_value",
"long_cnt", and "is_cycled" sequence columns used for?
I couldn't find anything in the docs or Google.

select * from test_id_seq;
sequence_name | last_value | increment_by | max_value
| min_value | cache_value | log_cnt | is_cycled |
is_called
---------------+------------+--------------+---------------------+-----------+-------------+---------+-----------+-----------
test_id_seq | 1 | 1 | 9223372036854775807 | 1 | 1 | 1
| f | f
(1 row)

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